1,3

The terms beyond a(3), found by PrimeForm, produce probable primes of lengths 24, 199, 1747 and 16474 digits. As both (8!)! and 2*((8!)!) each have the same number of digits, a(8) will correspond to a 168187-digit prime (by Bertrand's Postulate). For all n, if k > 1, then k >= nextprime(n!). As (8!)!+1 is composite, a(8) >= 40343.

a(3) = 7 as (3!)! + 7 = 6! + 7 = 720 + 7 = 727 is the smallest prime larger than (3!)!.

Sequence in context: A077586 A002614 A095885 this_sequence A123036 A142011 A074224

Adjacent sequences: A134053 A134054 A134055 this_sequence A134057 A134058 A134059

hard,more,nonn

Rick L. Shepherd (rshepherd2(AT)hotmail.com), Oct 04 2007